1. Field of the Invention
This invention relates to a device for opening and closing a door and more specifically, this invention relates to a device to effect multiple movements of a suspended door leaf.
2. Background of the Invention
In an overwhelming majority of situations, a door is opened and closed by hinges along the longitudinal edge of the door. This arrangement has unavoidable disadvantages. Specifically, as the door swings open or shut, the area included in a circular section, the radius of which is equal to the width of the door, must be free of all encumbrances. Longitudinally-hinged configurations also bring problems when thick doors are utilized, inasmuch as thicknesses have to be limited so as to allow clearance of the door edge with the door jamb. This disadvantage is most serious in such situations (shielding of radio frequency radiation or magnetic fields in particular) where one must ensure intimate and continuous contact between the door leaf and the walls of the enclosure or when the door leaf must bear some attachments or equipment that increase the effective thickness of the leaf.
Anechoic chambers are another case in point: the walls of the enclosure, the door leaf included, are covered with cones that normally project inwardly toward the center of the enclosure to distances of one meter or more. The use of much larger cones also is not unusual. Such protrusions makes the use of a door leaf extremely difficult to incorporate in a hinged door arrangement. To overcome this shortcoming, a regular thickness door is employed to initially seal the chamber, but then the door is covered with an absorber trolley containing the inwardly directed cones. As such, providing a door with anechoic surfaces requires two actions, first closing the door and then rolling the trolley in position. The same operation, in reverse, is required when exiting the anechoic room through the door opening.
Hinged door configurations suffer from other drawbacks. Specifically, where the axis of rotation defined by the hinges is vertical, the center of gravity of the door leaf is at some distance from that axis and thus the weight of the door produces a torque that must be counteracted by the hinges. This torque results in a gradual strain on the hinges with concomitant wear and tear of the hinges and misalignment of the door leaf. Also, because of the relatively large momentum of inertia of the edge-supported door leaf around the axis of rotation, motor-effected opening and closing of the leaf is often most cumbersome and expensive.
Finally, hinge-secured door leafs have the further disadvantage that they cannot be moved fully away from the door opening to allow adequate access to the door frame and surrounding elements of the enclosure wall. Examples of hinge secured door leafs include U.S. Pat. Nos. 4,486,980; 4,561,209; 4,953,324; and 5,013,869.
Several attempts have been made to overcome the aforementioned disadvantages in hinge-supported vertical door leafs. One method involves suspending the door from one or more wheels or glides. The wheels or glides are allowed to roll or slide on a horizontal rail to facilitate opening or closing the door. However, this configuration allows motion in only one rectilinear direction, which is perpendicular to the door opening, such movement indeed necessary when the leaf is particularly thick.
Other door configurations include a door leaf suspended from wheels that roll on a curved channel to impart door rotation around a vertical axis as the door is opened or closed. These arrangements suffer from the same disadvantages as hinge-supported doors, particularly when the leaf is more than a certain thickness.
Generally, motion in two rectilinear dimensions has proven to be much more difficult to effect, with multiple sets of rails, wheels or glides required. Heretofore, such arrangements have proven cumbersome especially when one seeks motorized transport of the door leaf inasmuch as two motors and/or a complex shifting mechanism are needed. (See e.g. U.S. Pat. No. 4,691, 581 and U.S. Pat. No. 4,753, 038. In the '038 patent, a door leaf is suspended from a rail which is in turn suspended from a perpendicular rail. The '038 patent requires that the door leaf pivot around a vertical axis and be supported by floor-mounted supports).
Systems, such as the ones discussed above where the door leaf is transported on ground-mounted rails have the additional disadvantage that additional supports must be provided to vertically maintain the door leaf. Also, ground mounted hardware, such as rails, impede access to the door and suffer damage as equipment is rolled over them. U.S. Pat. Nos. 4,644,690 and 4,753,038 disclose doors rolling on floor-mounted rails.
Two-dimensional or "dual movement" door motion is often required to effect unimpeded access to the door opening, particularly when "bulky" door configurations are utilized, such as in MRI- and Anechoic-applications.
A need exists in the art for a simple device to support and transport a door leaf in a plurality of positions. The configuration should be capable of multiple positioning of the leaf when a single channel, a single drive, and a single motor are utilized. The configuration should be particularly accommodating for heavy doors and bulky door designs, such as those incorporating thick dimensions in anechoic applications or movable panels for electromagnetic radiation shielding. The device should also be able to rely on only one means for positioning the door relative to an opening defined by a door jamb.